Buggy code:
class HostAdd extends AbstractAddStepHandler { static final HostAdd INSTANCE = new HostAdd ( ) ; private HostAdd ( ) { } @ Override protected void performRuntime ( OperationContext context , ModelNode operation , ModelNode model , ServiceVerificationHandler verificationHandler , List < ServiceController < ? > > newControllers ) throws OperationFailedException { final PathAddress address = PathAddress . pathAddress ( operation . get ( OP_ADDR ) ) ; final PathAddress serverAddress = address . subAddress ( 0 , ( ( address . size ( ) ) - 1 ) ) ; final PathAddress subsystemAddress = serverAddress . subAddress ( 0 , ( ( address . size ( ) ) - 1 ) ) ; final ModelNode subsystemModel = Tools . readModel ( context . readResourceFromRoot ( subsystemAddress ) ) ; final ModelNode fullModel = Tools . readModel ( context . readResource ( EMPTY_ADDRESS ) ) ; final String name = address . getLastElement ( ) . getValue ( ) ; final List < String > aliases = ALIAS . unwrap ( context , model ) ; final String defaultWebModule = DEFAULT_WEB_MODULE . resolveModelAttribute ( context , model ) . asString ( ) ; final Resource resource = context . readResource ( EMPTY_ADDRESS ) ; final Resource accessLog = resource . getChild ( PATH_ACCESS_LOG ) ; final String defaultServerName = DEFAULT_SERVER . resolveModelAttribute ( context , subsystemModel ) . asString ( ) ; final String serverName = serverAddress . getLastElement ( ) . getValue ( ) ; boolean installCommonHost = defaultServerName . equals ( serverName ) ; final ServiceName virtualHostServiceName = UndertowService . virtualHostName ( serverName , name ) ; final ServiceName accessLogServiceName = UndertowService . accessLogServiceName ( serverName , name ) ; <START_BUG> Host service = new Host ( name , ( aliases == null ? new LinkedList < String > ( ) : aliases ) , defaultWebModule ) ; <END_BUG> final ServiceBuilder < Host > builder = context . getServiceTarget ( ) . addService ( virtualHostServiceName , service ) . addDependency ( SERVER . append ( serverName ) , Server . class , service . getServerInjection ( ) ) . addDependency ( UNDERTOW , UndertowService . class , service . getUndertowService ( ) ) . addDependency ( ( accessLog != null ? REQUIRED : OPTIONAL ) , accessLogServiceName , AccessLogService . class , service . getAccessLogService ( ) ) ; builder . addListener ( verificationHandler ) ; builder . setInitialMode ( ON_DEMAND ) ; HostAdd . configureFilterRef ( fullModel , builder , service ) ; final ServiceController < WebHost > commonController = null ; if ( installCommonHost ) { addCommonHost ( context , verificationHandler , name , aliases , serverName , virtualHostServiceName ) ; } final ServiceController < Host > serviceController = builder . install ( ) ; final ServiceName consoleRedirectName = UndertowService . consoleRedirectServiceName ( serverName , name ) ; final ServiceController < ConsoleRedirectService > consoleServiceServiceController ; if ( ( context . getProcessType ( ) ) == ( ProcessType . STANDALONE_SERVER ) ) { final ConsoleRedirectService redirectService = new ConsoleRedirectService ( ) ; final ServiceBuilder < ConsoleRedirectService > redirectBuilder = context . getServiceTarget ( ) . addService ( consoleRedirectName , redirectService ) . addDependency ( SERVICE_NAME , HttpManagement . class , redirectService . getHttpManagementInjector ( ) ) . addDependency ( virtualHostServiceName , Host . class , redirectService . getHostInjector ( ) ) . setInitialMode ( PASSIVE ) ; consoleServiceServiceController = redirectBuilder . install ( ) ; } else { final ConsoleRedirectService redirectService = new ConsoleRedirectService ( ) ; final ServiceBuilder < ConsoleRedirectService > redirectBuilder = context . getServiceTarget ( ) . addService ( consoleRedirectName , redirectService ) . addDependency ( virtualHostServiceName , Host . class , redirectService . getHostInjector ( ) ) . setInitialMode ( PASSIVE ) ; consoleServiceServiceController = redirectBuilder . install ( ) ; } if ( newControllers != null ) { newControllers . add ( serviceController ) ; newControllers . add ( consoleServiceServiceController ) ; if ( installCommonHost ) { newControllers . add ( commonController ) ; } } } private ServiceController < WebHost > addCommonHost ( OperationContext context , ServiceVerificationHandler verificationHandler , String hostName , List < String > aliases , String serverName , ServiceName virtualHostServiceName ) { } private static void configureFilterRef ( final ModelNode model , ServiceBuilder < Host > builder , Host service ) { } }

Fix:
final Host service = new Host ( name , ( aliases == null ? new LinkedList < String > ( ) : aliases ) , defaultWebModule ) ;